JP3716614B2 - Optical scanning system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning system, and more particularly to an optical scanning system provided with a plurality of polygon motor units each including a polygon mirror and a polygon motor that rotationally drives the polygon mirror.
[0002]
[Prior art]
In an image recording apparatus that scans a recording medium with a light beam modulated with an image signal and records an image, a polygon mirror having a plurality of reflecting mirror surfaces on the outer periphery is used as a polygon motor as an optical scanning apparatus that scans the light beam. By rotating at a high speed and irradiating a predetermined position on the reflecting mirror surface of the polygon mirror, the incident angle of the light beam with respect to the reflecting mirror surface is changed with time, and the reflection direction of the light beam by the reflecting mirror surface is changed. It is widely used in general.
[0003]
Next, a configuration example of this type of conventional optical scanning device will be described with reference to FIGS. As shown in FIG. 9, the optical scanning device 10 includes a laser light generator 12 that generates a laser beam 14, and the laser beam 14 is emitted in the emission direction of the laser beam 14 from the laser light generator 12. A collimator lens 16 for parallel light and a polygon mirror 20 having a plurality of (eight in FIG. 9) reflecting mirror surfaces 21 on the outer periphery are sequentially arranged.
[0004]
The polygon mirror 20 is fixed to a rotary shaft 19 that is arranged in a polygon motor unit 18 so as to be rotatable about a fixed shaft (not shown). Further, the polygon motor unit can be rotated in the direction of arrow A in FIG. 9 by supplying a predetermined current to a rotation mechanism unit 40 (see also FIG. 10) described later in the polygon motor unit 18. 18 is configured. Further, the laser beam 14 emitted from the laser light generator 12 is modulated with image information of an image to be recorded.
[0005]
On the other hand, a condensing optical system 22 composed of an fθ lens or the like is disposed in the reflection direction of the laser beam 14 by the reflecting mirror surface 21 of the polygon mirror 20, and downstream of the laser beam 14 from the condensing optical system 22. In addition, a reflecting mirror 24 is disposed at a position where the laser beam 14 that passes slightly outside the scanning start position of the photosensitive drum 28, which will be described later, can be reflected. An SOS sensor 26 that outputs a predetermined detection signal when 14 incidents are detected is disposed.
[0006]
Further, a photosensitive drum 28 as a recording medium is disposed on the downstream side of the laser beam 14 from the condensing optical system 22 and outside the optical scanning device 10.
[0007]
As shown in FIG. 10A, the polygon motor unit 18 is provided with a drive control unit 42 for controlling the rotation mechanism of the polygon mirror 20, and the rotation speed of the polygon mirror 20 is provided at the CLK terminal of the drive control unit 42. Reference clock signal f having a frequency serving as a reference for_oIs input to the S / S terminal, and a start / stop signal indicating the start and end of the rotational drive of the polygon mirror 20 is input to the S / S terminal, and the polygon mirror 20 is stabilized at a desired rotational speed from the RDY terminal. A ready signal generated when the motor is rotating is output.
[0008]
On the other hand, the output end of the drive control unit 42 is connected to a rotation mechanism unit 40 including a polygon mirror 20 and a polygon motor that rotates the polygon mirror.
[0009]
As shown in FIG. 10B, the drive control unit 42 has a reference clock signal f at one input end._oIs input, the output end of the phase comparator 44 is connected to the input end of the phase corrector 46, and the output end of the phase corrector 46 is connected to the rotation drive unit 48. The output end of the rotation drive unit 48 is connected to a stator coil (not shown) of the rotation mechanism unit 40.
[0010]
On the other hand, the polygon motor unit 18 includes a speed detector 50, and the output end of the speed detector 50 is connected to the other input end of the phase comparator 44.
[0011]
In FIG. 10B, the start / stop signal and ready signal shown in FIG. 10A are not shown.
[0012]
Next, with reference to FIG. 9 and FIG. 11, the overall operation when optical scanning is performed by the optical scanning device 10 shown in FIG. 9 will be described. FIG. 11 is a plan view sequentially showing changes in the optical scanning state with time. In FIG. 9, the incident direction of the laser beam 14 with respect to the reflecting mirror surface of the polygon mirror 20 is the direction of the photosensitive drum 28. FIG. 11 shows a so-called front incidence type in which the laser beam 14 is incident from the direction of the photosensitive drum 28.
[0013]
First, the polygon mirror 20 is rotated at high speed in the direction of arrow A in FIG. Thereafter, a laser beam 14 is emitted from the laser light generator 12, modulated by a modulation means (not shown), and then incident on a reflecting mirror surface 21 (hereinafter referred to as a first reflecting mirror surface 21) of the polygon mirror 20.
[0014]
The laser beam 14 reflected by the first reflecting mirror surface 21 of the polygon mirror 20 is incident on the reflecting mirror 24 and then reflected and incident on the SOS sensor 26. At this time, a detection signal of the laser beam 14 is output from the SOS sensor 26 (see FIG. 11A). Based on the timing at which this detection signal is output from the SOS sensor 26, the starting point of the optical scanning is determined for each scanning. That is, the laser light generator 12 is controlled so that the emission start angle of the laser beam 14 is constant with reference to the timing at which the detection signal is output from the SOS sensor 26.
[0015]
Thereafter, as the polygon mirror 20 rotates in the direction of arrow A, the laser beam 14 gradually deflects in the traveling direction and scans on the photosensitive drum 28 (see FIGS. 11B and 11C).
[0016]
When the polygon mirror 20 further rotates and the next reflecting mirror surface 21 (hereinafter referred to as the second reflecting mirror surface 21) rotates, the laser beam 14 enters the second reflecting mirror surface 21 and the second reflecting mirror surface 21 is rotated. As with the first reflecting mirror surface 21 described above, the laser beam 14 is also deflected. At this time, the photosensitive drum 28 is rotated by a predetermined distance in the direction of arrow B in FIG. 9 while the laser beam 14 is scanned, so that the recording surface of the photosensitive drum 28 is moved in the direction of arrow C in FIG. Thus, the laser beam 14 reflected and deflected by the second reflecting mirror surface 21 is irradiated to a position slightly shifted from the scanning position of the laser beam 14 by the first reflecting mirror surface 21 (FIG. 11D and FIG. E)).
[0017]
In this manner, the laser beam 14 for each scan is not scanned at the same position on the photosensitive drum 28, but the surface of the photosensitive drum 28 is sequentially scanned, and an image (electrostatic) is applied to the surface of the photosensitive drum 28. Latent image) is recorded.
[0018]
Next, the operation of the polygon motor unit 18 shown in FIGS. 10A and 10B will be described.
[0019]
When the rotating body of the rotating mechanism unit 40 rotates, the speed detector 50 detects a speed detection signal f having a frequency proportional to the rotational speed._mIs output to the phase comparator 44. This speed detection signal f_mIs supplied by the phase comparator 44 to the reference clock signal f._oCompared with the speed difference signal Φ according to the phase difference of each signal_pIs output to the phase corrector 46.
[0020]
Speed difference signal Φ_pIs passed through the phase corrector 46 to cause a current control signal V_mAnd output to the rotation drive unit 48. In the rotation drive unit 48, the input current control signal V_mStator coil current I for rotating the rotating body of the rotating mechanism 40 based on the magnitude of_mTo control the current value.
[0021]
Here, if the speed detection signal f_mThe frequency of the reference clock signal f_oIf the frequency is lower than the frequency of the speed difference signal Φ output from the phase comparator 44_pAs a result, the rotational drive unit 48 causes the stator coil current I_mAnd the rotation of the rotating body of the rotating mechanism unit 40 is accelerated. On the other hand, on the contrary, the speed detection signal f_mThe frequency of the reference clock signal f_oThe stator coil current I_mIs reduced, and the rotation of the rotating body of the rotation mechanism 40 is decelerated. That is, the rotational speed of the rotating body of the rotating mechanism 40 is always converged to a constant value.
[0022]
By the way, if a plurality of the optical scanning devices 10 as described above are provided, it is obvious that the overall scanning speed is improved according to the number of the optical scanning devices 10. Considering the case of applying an optical scanning device to a color image forming apparatus that forms a color image, it is necessary to generate a laser beam for each element color and write an image, so optical scanning is performed for each element color. It can be said that the configuration for preparing the device is a very natural configuration. Accordingly, in high-speed printers, color copiers, and the like, it is common to install a plurality of optical scanning devices.
[0023]
FIG. 12 shows a configuration example of a color image forming apparatus including a plurality of optical scanning devices in this way. In the color image forming apparatus shown in the figure, an optical scanning device 10K and a photosensitive drum 28K, an optical scanning device 10C and a photosensitive drum 28C corresponding to each of four kinds of element colors (black, cyan, magenta, and yellow), An optical scanning device 10M and a photosensitive drum 28M, and an optical scanning device 10Y and a photosensitive drum 28Y are provided.
[0024]
Further, a transfer belt 30 is wound around a plurality of rollers at positions where images (electrostatic latent images) for each element color recorded on each of the four photosensitive drums 28K, 28C, 28M, and 28Y can be transferred. is set up.
[0025]
In this color image forming apparatus, after images are recorded on the photosensitive drums 28K, 28C, 28M, and 28Y for each element color, the transfer belt 30 is rotated in the direction of arrow D in FIG. 12 is transferred to the transfer belt 30, and the output paper 32 is moved in the direction of arrow E in FIG. 12 in synchronization with the timing at which the image transfer position on the transfer belt 30 is moved to the carry-in position of the output paper 32. As a result, a color image is formed on the output paper 32.
[0026]
In this way, when one image is formed by performing optical scanning in parallel by a plurality of optical scanning devices, the images obtained as a result of the optical scanning performed independently are combined, The optical scanning performed by each optical scanning device needs to be accurately performed according to a predetermined timing.
[0027]
FIG. 13B shows the state of the scanning latent image on the transfer belt 30 when each optical scanning device accurately performs optical scanning according to a predetermined timing in the color image forming apparatus shown in FIG. ing. As shown in the figure, in this case, a total of four polygon mirrors 20 (one in each of the optical scanning devices, in FIGS. 13A to 13C, polygon a, polygon b, polygon c, polygon) The interval in the sub-scanning direction (direction orthogonal to the scanning direction) of the scanning latent image by (d) is uniform, and as a result, a high-quality image can be formed.
[0028]
On the other hand, as shown in the timing chart of FIG. 13A, the scanning start timing of the laser beam of each of the four polygon mirrors is a reference signal T that serves as a reference for the scanning start by each polygon mirror._oIf the timing does not coincide with the rise timing of one cycle, the interval in the sub-scanning direction of the finally synthesized scanning latent image becomes non-uniform as shown in FIG. I will let you.
[0029]
This deviation in scanning start timing is caused by the rotation of the polygon mirrors provided in each optical scanning device in an irregular direction. In this specification, the amount of deviation in each polygon mirror is referred to as the rotational phase. Expressed in units of angles. That is, the rotation phase angle is based on the direction of the reflecting mirror surface of one polygon mirror at any reference timing, and how much the reflecting mirror surface of other polygon mirrors has advanced relative to this polygon mirror. Or, it is expressed as an angle whether it is delayed or not, and is usually a value obtained by multiplying the physical rotation angle by the number of reflecting mirror surfaces of the polygon mirror. For example, in the case of a polygon mirror having eight reflecting mirror surfaces, it returns to the initial state when it is physically deviated by 45 °, so the rotational phase angle when it is physically deviated by 22.5 ° is 180 °, Specifically, the rotational phase angle when shifted by 11.25 ° is 90 °. In FIG. 13A, Φ_ab, Φ_ac, And Φ_adCorresponds to the rotational phase angle of the polygon mirrors b, c, and d with the polygon mirror a as a reference.
[0030]
Thus, if the rotation phase angles of all the polygon mirrors are 0, the interval between the scanning latent images in the sub-scanning direction should be uniform, but in practice, the scanning latent is also determined by the distance between the optical scanning devices. Since the image interval differs, when the rotation phase angle of each polygon mirror matches the offset value determined by the arrangement of each optical scanning device, the interval between the scanning latent images becomes uniform, and a high quality image is formed. Will be able to.
[0031]
Therefore, usually, control is performed such that the rotational speed of the polygon motor that rotationally drives each polygon mirror is finely adjusted so as to be adjusted to a predetermined rotational phase angle. In this case, a method is generally adopted in which the pulse edge of the reference clock signal that determines the rotation speed of the polygon motor is individually controlled to change the rotation phase angle of each polygon mirror.
[0032]
FIG. 14 shows an example of the configuration of a conventional optical scanning system of this type (equipped with a plurality of optical scanning devices). As shown in the figure, in this optical scanning system, a reference signal generated individually from the main controller 60 for each of the four optical scanning devices 10K, 10C, 10M, and 10Y provided for each element color. 62K, 62C, 62M, and 62Y were supplied by independent wirings.
[0033]
[Problems to be solved by the invention]
However, in the conventional optical scanning system as shown in FIG. 14, since it is necessary to supply different reference signals to the respective optical scanning devices as described above, the reference signal is sent from the main controller to each optical scanning device. The number of wiring cables to be supplied is the same as the number of optical scanning devices, and as the number of optical scanning devices increases, the distance between the main controller and the optical scanning device increases, inevitably. Since the wiring cable becomes longer, there is a problem that as a result, it is easily affected by noise, and the number of work steps for assembling is increased, resulting in an increase in manufacturing cost.
[0034]
The present invention has been made to solve the above-described problems, and has an object to provide an optical scanning system that has high noise resistance and can simplify the number of work steps during assembly. .
[0035]
[Means for Solving the Problems]
  In order to achieve the above object, the optical scanning system according to claim 1 includes a plurality of polygon motor units each having a polygon mirror having a plurality of reflecting mirror surfaces and a polygon motor for rotationally driving the polygon mirror. An optical scanning system comprising:The pulse width is composed of a long pulse longer than a predetermined length and a short pulse whose pulse width is shorter than the predetermined length. The correspondence between each short pulse and each polygon motor unit is the number of times based on the long pulse. It is performed based on whether it is a short pulse, or the association between each pulse and each polygon motor unit is determined by the number of short pulses that are continuously input immediately before the long pulse,Reference signal generating means for generating a reference signal serving as a reference for controlling the direction of the reflecting mirror surface of the polygon mirrorEach of the plurality of polygon motor units is provided, and the reference signal is based on how many short pulses are associated with each short pulse and each polygon motor unit based on the long pulse. If the detected pulse is a long pulse, the count value of the counter that counts the number of short pulses is reset. If the detected pulse is a short pulse, the pulse is detected. After incrementing the counter and generating a reference clock signal for controlling the rotation drive of the polygon mirror when the count value of the counter reaches a value corresponding to the arrangement order of the polygon motor units, the count value of the counter While the reference signal indicates that the correspondence between each pulse and each polygon motor unit is the long pulse. If it is determined by the number of short pulses input continuously in advance, each pulse of the reference signal is detected. If the detected pulse is a short pulse, the counter is incremented and the detected pulse is detected. Is a long pulse, and if the count value of the counter is equal to the value corresponding to the arrangement order of the polygon motor unit, the count value of the counter is reset after generating the reference clock signal, and the detected pulse is a long pulse. And a plurality of reference clock signal generating means for resetting the count value of the counter when the count value of the counter is not equal to the value corresponding to the arrangement order of the polygon motor units,And the same reference signal generated by the reference signal generation means is supplied to at least two of the polygon motor units.
[0036]
  The optical scanning system according to claim 1 includes a plurality of polygon motor units each having a polygon mirror having a plurality of reflecting mirror surfaces and a polygon motor that rotationally drives the polygon mirror.The pulse width is composed of a long pulse longer than a predetermined length and a short pulse whose pulse width is shorter than the predetermined length. The correspondence between each short pulse and each polygon motor unit is the number of times based on the long pulse. It is performed based on whether it is a short pulse, or the association between each pulse and each polygon motor unit is determined by the number of short pulses that are continuously input immediately before the long pulse,A reference signal serving as a reference for controlling the direction of the reflecting mirror surface of the polygon mirror is generated by the reference signal generating means, and the same reference signal generated by the reference signal generating means is supplied to at least two of the polygon motor units. Is done.
On the other hand, in the polygon motor unit to which the same reference signal is supplied, the reference clock signal generation means causes the reference signal to be associated with each short pulse and each polygon motor unit at the shortest number based on the long pulse. If it is based on whether it is a pulse, each pulse of the reference signal is detected, and if the detected pulse is a long pulse, the count value of the counter that counts the number of short pulses is reset and detected If the pulse is a short pulse, the counter is incremented, and the reference clock for controlling the rotational drive of the polygon mirror when the count value of the counter reaches the value corresponding to the arrangement order of the polygon motor unit After the signal is generated, the count value of the counter is reset, while the reference signal is When the association with the Lygon motor unit is determined by the number of short pulses that are continuously input immediately before the long pulse, each pulse of the reference signal is detected, and the detected pulse is a short pulse. If the counter is incremented, the detected pulse is a long pulse, and if the count value of the counter is equal to the value corresponding to the arrangement order of the polygon motor units, the reference clock signal is generated. When the count value of the counter is reset and the detected pulse is a long pulse and the count value of the counter is not equal to the value corresponding to the arrangement order of the polygon motor units, the count value of the counter is reset .
[0037]
Therefore, in the polygon motor unit to which the same reference signal is simultaneously supplied, the direction of the reflecting mirror surface can be accurately controlled, and optical scanning can be performed at an accurate timing. The signal line connection form for supplying the same reference signal from the reference signal generating means to at least two polygon motor units includes a daisy chain connection, a branching connection, a main line / branch line connection, etc. Can be applied.
[0038]
  As described above, according to the optical scanning system of the first aspect, for at least two of the plurality of polygon motor units.The pulse width is longer than a predetermined length and the short pulse is shorter than the predetermined length, and the correspondence between each short pulse and each polygon motor unit is based on the long pulse. Or the correspondence between each pulse and each polygon motor unit is determined by the number of short pulses continuously input immediately before the long pulse.Since the same reference signal generated is supplied, the length of the connection line for supplying the same reference signal can be shortened, the noise resistance can be increased, and the assembling can be performed. Work man-hours can be simplified.
[0039]
According to a second aspect of the present invention, in the optical scanning system according to the first aspect, the reference signal generated by the reference signal generating means may be used as a reference signal for controlling the rotational speed of each polygon motor. It is characterized by use.
[0040]
According to the optical scanning system of the second aspect, the reference signal generated by the reference signal generating means according to the first aspect of the invention is also used as a reference signal for controlling the rotational speed of each polygon motor.
[0041]
As described above, according to the optical scanning system of the second aspect, the same effect as that of the first aspect of the invention can be obtained, and in the polygon motor unit to which the same reference signal is input, the input reference signal Since the rotation speed of the polygon mirror can also be controlled by this, a circuit required for controlling the rotation speed can be omitted.
[0042]
According to a third aspect of the present invention, in the optical scanning system according to the second aspect, in each of the plurality of polygon motor units to which the same reference signal is supplied, each polygon mirror has an orientation of a reflecting mirror surface. The change can be made individually, and the change amount and change timing are instructed by the same reference signal.
[0043]
According to the optical scanning system of the third aspect, in the plurality of polygon motor units to which the same reference signal of the optical scanning system of the second aspect is supplied, the polygon mirrors of the polygon mirror units respectively have the directions of the reflecting mirror surfaces individually. The change can be made, and the change amount and change timing are instructed by the same reference signal.
[0044]
Thus, according to the optical scanning system of the third aspect, the same effect as that of the second aspect of the invention can be obtained, and a plurality of polygons to which the same reference signal in the second aspect of the invention is supplied are provided. The direction of the reflecting mirror surface of the polygon mirror each motor unit has can be individually changed, and the change amount and change timing are instructed by the same reference signal, so only by changing the reference signal, Only the direction of the reflecting mirror surface of each polygon mirror of the polygon motor unit to which the same reference signal is supplied can be controlled.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0046]
[First Embodiment]
First, the configuration of the optical scanning system according to the first embodiment will be described with reference to FIG.
[0047]
As shown in the figure, the optical scanning system according to the first embodiment includes a main controller 60 that controls the entire optical scanning system, and the output end of the main controller 60 that outputs the phase reference signal α is The four optical scanning devices 10K, 10C, 10M, and 10Y that form images corresponding to the four types of element colors (black, cyan, magenta, and yellow) are connected in a branched manner. The main controller 60 is connected to an output terminal that outputs a phase signal β indicating the phase of the optical scanning device 10K. The main controller 60 receives the phase signal β input from the optical scanning device 10K and the main controller 60. A phase reference signal α is generated based on the clock 64 and supplied to each optical scanning device by a branching connection.
[0048]
Photosensitive drums 28K, 28C, 28M, and 28Y are respectively arranged in the emission directions of the respective laser beams 14 deflected by the four optical scanning devices 10, and the four photosensitive drums 28 are arranged on the four photosensitive drums 28, respectively. The transfer belt 30 is disposed so as to be able to come into contact. The transfer belt 30 can transfer the images (electrostatic latent images) formed on the four photosensitive drums 28 by moving in the direction of arrow D in FIG.
[0049]
Here, in the optical scanning system according to the first embodiment, as shown in FIG. 13B, the intervals in the sub-scanning direction of all scanning latent images transferred onto the transfer belt 30 are made substantially uniform. The arrangement interval between each optical scanning device 10 and each photosensitive drum 28, the conveyance speed of the transfer belt 30, and the like are adjusted in advance.
[0050]
Further, inside the four optical scanning devices 10, there are provided switches (not shown) for switching whether or not to use the supplied phase reference signal α as a reference for the rotation phase angle. The optical scanning device to be controlled can be selected in advance.
[0051]
In the optical scanning system configured as described above, after the optical scanning is performed on the corresponding photosensitive drum 28 by the optical scanning device 10 previously selected by the switch (not shown), the transfer belt 30 is moved to the arrow shown in FIG. The electrostatic latent image formed on the photosensitive drum 28 by moving in the D direction is transferred to the transfer belt 30.
[0052]
As described above, in the optical scanning device 10 according to the first embodiment, the signal lines for supplying the same phase reference signal α to the plurality of optical scanning devices 10 are connected in a branched manner. As a result, the length of the signal line can be shortened, noise resistance can be increased, and the number of work steps during assembly can be simplified.
[0053]
In the first embodiment, the connection form between the main controller and the four optical scanning devices has been described as a branched connection as shown in FIG. 1A. However, the present invention is not limited to this. For example, the connection form as shown in FIG. 1B is not limited, and the same effect as this embodiment, that is, the length of the signal line can be shortened, and the noise resistance can be increased. In addition, it is possible to produce an effect that the number of work steps during assembly can be simplified.
[0054]
In FIG. 1B, the same speed reference signal γ serving as a reference for the rotational speed is supplied from the main controller 60 to each optical scanning device by a branching type connection, and the phase reference signal α serving as a phase reference is daisy-chained. A configuration example in the case of supplying to each optical scanning device by a chain connection is shown.
[0055]
[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
[0056]
As shown in the figure, the optical scanning system according to the second embodiment supplies a reference signal 62 that serves as a reference for the phase and rotational speed of each optical scanning device to each optical scanning device through a daisy chain connection. Yes.
[0057]
Therefore, in the optical scanning system according to the second embodiment, the length of the signal line can be shortened and the noise resistance can be further increased and the assembly can be performed as compared with the first embodiment. It is possible to further simplify the work man-hour at the time.
[0058]
In the optical scanning system according to the second embodiment, each optical scanning device 10 does not need to have a signal source for determining the rotational speed of the polygon motor, and a polygon motor driving circuit for rotating the polygon mirror is provided. In addition to simplification, the rotational speed and rotational phase of each optical scanning device 10 can be controlled simultaneously and dynamically, and fine adjustment of the scanning line position can be performed during operation.
[0059]
In the second embodiment, the case where the connection form between the main controller and the four optical scanning devices is a daisy chain connection has been described. However, the present invention is not limited to this, and the main line / The length of the signal line can be shortened as a branch type connection, etc., and the noise resistance can be increased, and the work man-hours during assembly can be simplified. it can.
[0060]
[Third Embodiment]
Next, a third embodiment of the present invention will be described. The overall configuration of the optical scanning system according to the third embodiment is the same as that shown in FIG.
[0061]
First, the configuration in the four optical scanning devices 10 (see also FIG. 2) will be described with reference to FIG. As shown in the figure, each optical scanning device 10 is provided with a polygon motor unit 18 ', and the polygon motor unit 18' includes a pulse width discriminator 70 to which a reference signal 62 from the previous stage is input. It has been.
[0062]
One output terminal of the pulse width discriminator 70 is connected to the input terminal of the long pulse counter 72, and the output terminal of the long pulse counter 72 is connected to one input terminal of the reference clock generator 76. On the other hand, the other output terminal of the pulse width discriminator 70 is connected to the input terminal of the short pulse counter 74, and the output terminal of the short pulse counter 74 is connected to the other input terminal of the reference clock generator 76. Note that an external clock is input to the reference clock generator 76, and the reference clock generator 76 operates based on this external clock.
[0063]
Further, the output terminal of the reference clock generator 76 is connected to the CLK terminal of the drive control unit 42. In addition, since the structure of the drive control unit 42 in this 3rd Embodiment and the rotation mechanism part 40 is the same as that of what was shown in FIG. 10, description here is abbreviate | omitted.
[0064]
On the other hand, each optical scanning device 10 is provided with a buffer 78 to which the reference signal 62 from the previous stage is input, and the output end of the buffer 78 is connected to the optical scanning device 10 at the next stage. As is apparent from FIG. 2, the preceding stage and the next stage described above are the main controller 60 and the next stage is the optical scanning apparatus 10C when the target optical scanning apparatus is the optical scanning apparatus 10K. In the case where the target optical scanning device is the optical scanning device 10C, the previous stage is the optical scanning device 10K and the next stage is the optical scanning device 10M, and the target optical scanning device is the optical scanning device 10M. The preceding stage is the optical scanning apparatus 10C and the next stage is the optical scanning apparatus 10Y. Further, when the target optical scanning apparatus is the optical scanning apparatus 10Y, the preceding stage is the optical scanning apparatus 10M and there is no next stage.
[0065]
As shown in FIG. 4, the reference signal 62 according to the third embodiment includes a pulse having a pulse width longer than a predetermined length (hereinafter referred to as a long pulse) and a pulse having a pulse width shorter than the predetermined length ( Hereinafter, each short pulse is a reference for the rotational phase angle in each optical scanning device 10. Further, the correspondence between each short pulse and each optical scanning device 10 is performed based on how many short pulses are based on the long pulse. That is, for example, the second short pulse after the long pulse is the rotational phase angle Φ of the optical scanning device 10C with respect to the optical scanning device 10K._1-2Similarly, the fourth short pulse is the rotational phase angle Φ of the optical scanning device 10Y with respect to the optical scanning device 10K._1-4Means.
[0066]
Further, the arrangement position of each optical scanning device 10 according to the third embodiment is such that the scanning latent image synthesized on the transfer belt 30 in the sub-scanning direction when the rotational phase angle of each polygon motor is shifted by 90 °. The interval is adjusted in advance so as to be substantially uniform.
[0067]
Next, the operation of the polygon motor unit 18 'shown in FIG. 3 will be described. The count values of the long pulse counter 72 and the short pulse counter 74 in the polygon motor unit 18 'are initialized before the operation starts.
[0068]
The reference signal 62 input from the optical scanning device 10 (or the main controller 60) in the previous stage is input to the pulse width discriminator 70 and the buffer 78, respectively. The reference signal 62 input to the buffer 78 is changed in signal level by the buffer 78. It is adjusted to an appropriate size and output to the optical scanning device 10 at the next stage. If the polygon motor unit 18 'is of the optical scanning device 10Y, there is no next stage, so that no output signal is supplied anywhere.
[0069]
In the pulse width discriminator 70, the pulse width of each pulse of the input reference signal 62 is compared with the predetermined length, and if it is longer than the predetermined length, a count trigger signal is output to the long pulse counter 72 and is short. In this case, a count trigger signal is output to the short pulse counter 74.
[0070]
In the long pulse counter 72 and the short pulse counter 74, the count value is incremented every time the count trigger signal from the pulse width discriminator 70 is input, and when the count value reaches a predetermined set value, the count completion signal is used as the reference clock. It is output to the generator 76. In this embodiment, the setting value for the long pulse counter 72 is 1, and the setting value for the short pulse counter 74 is a value corresponding to the arrangement order of the optical scanning device 10, that is, for example, the optical scanning device is an optical scanning device. 1 is set for 10K, and 3 is set for the optical scanning device 10M.
[0071]
In the reference clock generator 76, the reference clock signal f is based on the count completion signals input from the long pulse counter 72 and the short pulse counter 74._oIs generated and output to the drive control unit 42. In the drive control unit 42, the rotation drive of the rotation mechanism 40 is controlled by the same operation as that shown in FIG.
[0072]
With the above operation, the reference clock signal f output from the reference clock generator 76 in each optical scanning device 10 to the drive control unit 42._oAs shown in FIG. 4, the signal is a timing corresponding to the rotational phase angle of each optical scanning device 10.
[0073]
Although the present embodiment is realized by an electronic circuit, completely equivalent functions can also be realized by using a microprocessor or the like. The flow of processing in this case is approximately that shown in the flowchart of FIG.
[0074]
First, in step 100 of FIG. 5, the detection of the pulse of the reference signal 62 is waited, and when a pulse is detected, an affirmative determination is made and the routine proceeds to step 102.
[0075]
In step 102, it is determined whether the pulse width of the detected pulse is longer or shorter than the predetermined length. If it is longer, the process proceeds to step 110 to count the number of short pulses (in FIG. 3, the short pulse counter 74). After the count value is reset, the process returns to step 100.
[0076]
On the other hand, if it is determined in step 102 that the pulse width of the pulse detected in step 100 is shorter than the predetermined length, the process proceeds to step 104, the counter is incremented, and then the process proceeds to step 106. Step 100, step 102, step 104, and step 110 correspond to the operation of the pulse width discriminator 70 in FIG.
[0077]
In step 106, it is determined whether or not the count value of the counter has reached a preset number of times. If not reached, the process returns to step 100, and if reached, the process proceeds to step 108. The number of times set in advance at this time is a number indicating the arrangement order of the optical scanning device 10 including the polygon motor unit 18 ′. For example, when the target optical scanning device is the optical scanning device 10K, the number is 1 In the case where the target optical scanning device is the optical scanning device 10C, the value is 2.
[0078]
In step 108, the reference clock signal f_o(Corresponding to the operation of the reference clock generator 76 in FIG. 3) and output to the drive control unit. In the next step 110, the count value of the counter is reset, and then the process returns to step 100.
[0079]
Note that the polygon motor unit 18 ′ shown in FIG. 3 can be realized with the simple configuration shown in FIG. 6.
[0080]
80 to 90 in the figure are parts for operating the pulse width discriminator 70 in FIG. Reference numerals 92 and 94 are portions for operating the short pulse counter 74 in FIG. 3, and can output four types of reference signals. Note that the long pulse counter 72 in FIG. 3 is not included in FIG. 6 because it is not necessary in this embodiment. Reference numeral 96 denotes a part for operating the reference clock generator 76 in FIG. 3, which is processed so that the duty ratio of the pulse signal output from the preceding shift register 92 is approximately 50%. The reference clock generator 76 may have functions such as noise removal and signal level stabilization in addition to the above-described change of the duty ratio.
[0081]
As described above in detail, in the optical scanning system according to the third embodiment, the signal lines for inputting the reference signal 62 to the plurality of optical scanning devices 10 are connected by daisy chain connection. As a result, the length of the signal line can be shortened, noise resistance can be increased, and the number of work steps during assembly can be simplified.
[0082]
Further, in the optical scanning system according to the third embodiment, signals corresponding to the number of the optical scanning devices 10 are superimposed and used as one reference signal 62, so that a plurality of optical scanning devices 10 are apparently substantially at the same time. Can be controlled.
[0083]
[Fourth Embodiment]
In the fourth embodiment, as the reference signal 62, a pulse train made up of pulses having two kinds of long and short pulse widths as shown in FIG. 7 is used. Further, the arrangement positions of the respective optical scanning devices 10 according to the fourth embodiment are synthesized on the transfer belt 30 when the rotational phase angles of the respective polygon motors are shifted by 90 °, as in the third embodiment. The interval between the scanning latent images in the sub-scanning direction is adjusted in advance so as to be substantially uniform.
[0084]
The reference signal 62 shown in FIG. 7 includes a pulse having a pulse width longer than a predetermined length (hereinafter referred to as a long pulse) and a pulse having a pulse width shorter than the predetermined length (hereinafter referred to as a short pulse). The signal edge of the long pulse falling immediately after the short pulse is a reference for the rotational phase angle of each optical scanning device 10.
[0085]
In addition, the correspondence between these pulses and each optical scanning device 10 is determined by the number of short pulses that are continuously input immediately before the long pulse. That is, for example, if the number of short pulses sandwiched between two long pulses is 3, the subsequent long pulse is a reference for the rotational phase angle of the optical scanning device 10M, and similarly if the number of short pulses is 1. The subsequent long pulse becomes the reference for the rotational phase angle of the optical scanning device 10K.
[0086]
Other configurations are substantially the same as those of the third embodiment, except that the set value of the long pulse counter 72 in FIG. 3 is 2 and the reference clock generator 76 controls the drive. Reference clock signal f to be output to unit 42₀This is only the operation sequence when generating. More specifically, in the third embodiment, the reference clock signal f is synchronized with the count end signal output from the short pulse counter 74.₀In the fourth embodiment, the reference clock signal f is synchronized with the count end signal output from the long pulse counter 72.₀Is output.
[0087]
Although the present embodiment is realized by an electronic circuit, completely equivalent functions can also be realized by using a microprocessor or the like. The flow of processing in this case is approximately that shown in the flowchart of FIG.
[0088]
First, in step 200, the detection of the pulse of the reference signal 62 is waited, and when a pulse is detected, an affirmative determination is made and the routine proceeds to step 202.
[0089]
In step 202, it is determined whether the pulse width of the detected pulse is longer or shorter than the predetermined length. If the pulse width is shorter, the process proceeds to step 204, the counter for counting short pulses is incremented, and then the process returns to step 200. .
[0090]
On the other hand, if it is determined in step 202 that the pulse width of the pulse detected in step 200 is longer than the predetermined length, the process proceeds to step 206 and the value of the counter is substituted for n. , N is equal to a preset setting value, the process proceeds to step 210 if equal, and the process proceeds to step 212 if not equal. Note that the preset setting value at this time is a number indicating the arrangement order of the optical scanning device 10, for example, 1 when the optical scanning device is the optical scanning device 10K, and the optical scanning device is the optical scanning device 10C. The case is 2.
[0091]
In step 210, the reference clock signal f_oIs output to the drive control unit. In the next step 212, the count value of the counter is reset, and then the process returns to step 200.
[0092]
As described above in detail, in the optical scanning system according to the fourth embodiment, the signal line for inputting the reference signal 62 to the plurality of optical scanning devices 10 is connected by daisy chain connection. As a result, the length of the signal line can be shortened, noise resistance can be increased, and the number of work steps during assembly can be simplified.
[0093]
Further, in the optical scanning system according to the fourth embodiment, signals corresponding to the number of the optical scanning devices 10 are superimposed and used as one reference signal 62, so that a plurality of optical scanning devices 10 are apparently substantially simultaneously. Can be controlled.
[0094]
In the third and fourth embodiments, the case where the reference signal is shown in FIGS. 4 and 7 has been described. However, the present invention is not limited to this, and the reference signal is not limited to each optical scanning device. Needless to say, it is possible to apply any number of reference signals that satisfy this condition.
[0095]
In each of the above embodiments, the case where the optical scanning system of the present invention is applied to a color image forming apparatus has been described. However, the present invention is not limited to this, and the present invention uses a plurality of optical scanning apparatuses. For example, the present invention may be applied to an image reading apparatus that reads an image recorded on an image carrier.
[0096]
【The invention's effect】
  According to the first aspect of the present invention, for at least two of the plurality of polygon motor unitsThe pulse width is longer than a predetermined length and the short pulse is shorter than the predetermined length, and the correspondence between each short pulse and each polygon motor unit is based on the long pulse. Or the correspondence between each pulse and each polygon motor unit is determined by the number of short pulses continuously input immediately before the long pulse.Since the same reference signal generated is supplied, the length of the connection line for supplying the same reference signal can be shortened, the noise resistance can be increased, and the assembling can be performed. The effect that the work man-hour can be simplified is obtained.
[0097]
According to the second aspect of the present invention, the same effect as that of the first aspect of the invention can be obtained. In the polygon motor unit to which the same reference signal is input, the polygon mirror is generated by the input reference signal. Therefore, the circuit required for controlling the rotation speed can be omitted.
[0098]
Furthermore, according to the invention described in claim 3, the same effects as in the invention described in claim 2 can be obtained, and a plurality of polygon motor units to which the same reference signal in the invention described in claim 2 is supplied are provided. Since the direction of the reflecting mirror surface of each polygon mirror can be individually changed, and the change amount and change timing are instructed by the same reference signal, the same reference can be changed only by changing the reference signal. There is an effect that only the direction of the reflecting mirror surface of each polygon mirror of the polygon motor unit to which the signal is supplied can be controlled.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a schematic configuration of an optical scanning system according to a first embodiment.
FIG. 2 is a configuration diagram showing a schematic configuration of an optical scanning system according to a second embodiment.
FIG. 3 is a block diagram showing a configuration of a polygon motor unit in an optical scanning device according to third and fourth embodiments.
FIG. 4 is a timing chart showing a state of a reference signal and a state of a reference clock signal generated inside the polygon motor unit using the reference signal in the third embodiment.
FIG. 5 is a flowchart showing an operation procedure of a polygon motor unit in each optical scanning device according to a third embodiment.
FIG. 6 is a configuration diagram showing an example of a more specific configuration of a polygon motor unit according to a third embodiment.
FIG. 7 is a timing chart showing a state of a reference signal and a state of a reference clock signal generated inside the polygon motor unit using the reference signal in the fourth embodiment.
FIG. 8 is a flowchart showing an operation procedure of a polygon motor unit in each optical scanning device according to a fourth embodiment.
FIG. 9 is a configuration diagram illustrating a configuration of an optical scanning device in a conventional image forming apparatus.
10A is a configuration diagram showing a configuration of a polygon motor unit in a conventional optical scanning device, and FIG. 10B is a configuration diagram showing a configuration of a drive control unit shown in FIG.
FIGS. 11A and 11B are plan views sequentially illustrating changes in the state of optical scanning with time in a conventional optical scanning device. FIGS.
FIG. 12 is a configuration diagram showing a schematic configuration of an optical scanning system when a plurality of conventional optical scanning devices are used.
FIG. 13A is a timing chart showing an example of a conventional reference signal, the operation timing of each polygon mirror, and the rotation phase angle of each polygon mirror, and FIG. 13B shows all the rotation phase angles of each polygon mirror. FIG. 6C is a schematic diagram showing a state of a scanning latent image on the transfer belt when 0, and FIG. 8C is a scanning latent image on the transfer belt when the rotation phase angle of each polygon mirror is shifted as shown in FIG. It is the schematic which shows the state of an image.
FIG. 14 is a configuration diagram showing a connection state in an optical scanning system when a plurality of conventional optical scanning devices are used.
[Explanation of symbols]
10 Optical scanning device
12 Laser light generator
18 Polygon motor unit
20 Polygon mirror
21 Reflective mirror surface
28 Photosensitive drum
40 Rotating mechanism
42 Drive control unit
44 Phase comparator
46 Phase corrector
48 Rotation drive
50 Speed detector
60 Main controller (reference signal generating means)
62 Reference signal
70 Pulse width identifier
72 Long pulse counter
74 Short pulse counter
76 Reference clock generator

Claims (3)

An optical scanning system comprising a plurality of polygon motor units each having a polygon mirror having a plurality of reflecting mirror surfaces and a polygon motor for rotationally driving the polygon mirror,
The pulse width is composed of a long pulse longer than a predetermined length and a short pulse whose pulse width is shorter than the predetermined length. The correspondence between each short pulse and each polygon motor unit is the number of times based on the long pulse. The polygon mirror of the polygon mirror is determined based on whether the pulse is a short pulse, or the correspondence between each pulse and each polygon motor unit is determined by the number of short pulses input immediately before the long pulse . Reference signal generating means for generating a reference signal serving as a reference for controlling the direction of the reflecting mirror surface ;
Each of the plurality of polygon motor units is provided, and the reference signal is determined based on how many short pulses are associated with each short pulse and each polygon motor unit based on the long pulse. In some cases, each pulse of the reference signal is detected. If the detected pulse is a long pulse, the counter value for counting the number of short pulses is reset. If the detected pulse is a short pulse, the counter is reset. Incrementing and generating a reference clock signal for controlling the rotation drive of the polygon mirror when the count value of the counter reaches a value corresponding to the arrangement order of the polygon motor unit, then resets the count value of the counter On the other hand, the reference signal corresponds to each pulse and each polygon motor unit immediately before the long pulse. If it is determined by the number of short pulses that are input continuously, each pulse of the reference signal is detected, and if the detected pulse is a short pulse, the counter is incremented. If the counter value is equal to the value corresponding to the arrangement order of the polygon motor unit, the counter value is reset after generating the reference clock signal, and the detected pulse is a long pulse. A plurality of reference clock signal generating means for resetting the counter value when the counter value is not equal to the value corresponding to the arrangement order of the polygon motor units;
With
An optical scanning system for supplying the same reference signal generated by the reference signal generation means to at least two of the polygon motor units.   2. The optical scanning system according to claim 1, wherein the reference signal generated by the reference signal generating means is also used as a reference signal for controlling the rotation speed of each polygon motor.   In the plurality of polygon motor units to which the same reference signal is supplied, each polygon mirror can change the direction of the reflecting mirror surface individually, and the change amount and change timing instructions are the same as those described above. The optical scanning system according to claim 2, wherein the optical scanning system is performed based on a reference signal of

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